The determination of body weight and its fluctuations of hospitalized and disabled patients is often of great importance, particularly, in cases of actual or impending electrolyte and water imbalance. This determination supplements laboratory data, makes their interpretation easier, more accurate, more relevant and more meaningful. It provides the clinical observer with objective information which may prove vital for proper and successful treatment.
Because of the patient's disability, it is often necessary to weigh the patient while supporting him in a sitting position. So-called chair scales have in the past been employed therefor. The horizontal sitting surface of the chair together with a backrest and lateral arm rests provide the necessary patient support. Although it represents no problem for a fit and healthy person to sit down on and to alight himself from the chair, for disabled or injured persons this task might be difficult or impossible. To facilitate the patient movement, prior art chair scales have incorporated arm rests that could be opened. Generally speaking, such arm rests could be opened to a limited extent, say over an arc of 45.degree.-60.degree. from the normal closed position. In other prior art scales the arm rest could be completely removed to facilitate the egress or ingress of a patient.
The former type of chair scale has the disadvantage that the arm rest, when pivoted into its open position, protrudes laterally and constitutes an obstacle to passerbys. Furthermore, it obstructed the lateral access to the chair. More importantly, the laterally protruding arm rest makes it difficult or impossible to position the chair scale against a patient's bed for the transfer of the patient from the bed to the chair by slidably moving him laterally onto the chair.
Chair scales having completely removable arm rests eliminate the problems caused by laterally protruding arm rests. However, such chairs are cumbersome to handle and attendants can forget to replace the arm rest during the weighing operation. Since the arm rest forms part of the chair scale's deadweight, its unaccounted removal leads to an inaccurate weighing. Such chair scales are therefore relatively undesirable.
Lastly, chair scales without any arm rests eliminate the problems of either one of the previously discussed scales. However, such chair scales do not provide lateral patient support which, in many instances, is mandatory to prevent the patient from slumping sideways and possibly falling from the chair.
Accordingly, prior art chair scales have operational disadvantages which, in the past, have not been fully overcome.